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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1996, 1997, 1998, 1999
* Sleepycat Software. All rights reserved.
*/
#include "db_config.h"
#ifdef HAVE_MUTEX_TAS
#ifndef lint
static const char sccsid[] = "@(#)mut_tas.c 11.4 (Sleepycat) 10/1/99";
#endif /* not lint */
#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#ifndef _MSC_VER /* _WIN32 */
#include <unistd.h>
#endif
#endif
#include "db_int.h"
#ifdef HAVE_MUTEX_68K_GCC_ASSEMBLY
#include "68K.gcc"
#endif
#ifdef HAVE_MUTEX_ALPHA_GCC_ASSEMBLY
#include "alpha.gcc"
#endif
#ifdef HAVE_MUTEX_HPPA_GCC_ASSEMBLY
#include "parisc.gcc"
#endif
#ifdef HAVE_MUTEX_SCO_X86_CC_ASSEMBLY
#include "sco.cc"
#endif
#ifdef HAVE_MUTEX_SPARC_GCC_ASSEMBLY
#include "sparc.gcc"
#endif
#ifdef HAVE_MUTEX_X86_GCC_ASSEMBLY
#include "x86.gcc"
#endif
#ifdef DIAGNOSTIC
#undef MSG1
#define MSG1 "mutex_lock: ERROR: lock currently in use: pid: %lu.\n"
#undef MSG2
#define MSG2 "mutex_unlock: ERROR: lock already unlocked\n"
#ifndef STDERR_FILENO
#define STDERR_FILENO 2
#endif
#endif
/*
* CDB___db_tas_mutex_init --
* Initialize a MUTEX.
*
* PUBLIC: int CDB___db_tas_mutex_init __P((DB_ENV *, MUTEX *, u_int32_t));
*/
int
CDB___db_tas_mutex_init(dbenv, mutexp, flags)
DB_ENV *dbenv;
MUTEX *mutexp;
u_int32_t flags;
{
memset(mutexp, 0, sizeof(*mutexp));
/*
* If this is a thread lock or the process has told us that there are
* no other processes in the environment, use thread-only locks, they
* are faster in some cases.
*
* This is where we decide to ignore locks we don't need to set -- if
* the application isn't threaded, there aren't any threads to block.
*/
if (LF_ISSET(MUTEX_THREAD) || F_ISSET(dbenv, DB_ENV_PRIVATE)) {
if (!F_ISSET(dbenv, DB_ENV_THREAD)) {
F_SET(mutexp, MUTEX_IGNORE);
return (0);
}
F_SET(mutexp, MUTEX_THREAD);
}
/* Initialize the lock. */
if (MUTEX_INIT(&mutexp->tas))
return (CDB___os_get_errno());
mutexp->spins = CDB___os_spin();
return (0);
}
/*
* CDB___db_tas_mutex_lock
* Lock on a mutex, logically blocking if necessary.
*
* PUBLIC: int CDB___db_tas_mutex_lock __P((MUTEX *));
*/
int
CDB___db_tas_mutex_lock(mutexp)
MUTEX *mutexp;
{
u_long ms;
int nspins;
if (!DB_GLOBAL(db_mutexlocks) || F_ISSET(mutexp, MUTEX_IGNORE))
return (0);
ms = 1;
loop: /* Attempt to acquire the resource for N spins. */
for (nspins = mutexp->spins; nspins > 0; --nspins) {
if (!MUTEX_SET(&mutexp->tas))
continue;
#ifdef DIAGNOSTIC
if (mutexp->locked != 0) {
char msgbuf[128];
(void)snprintf(msgbuf,
sizeof(msgbuf), MSG1, (u_long)mutexp->locked);
(void)write(STDERR_FILENO, msgbuf, strlen(msgbuf));
}
mutexp->locked = (u_int32_t)getpid();
#endif
if (ms == 1)
++mutexp->mutex_set_nowait;
else
++mutexp->mutex_set_wait;
return (0);
}
/* Yield the processor; wait 1ms initially, up to 1 second. */
CDB___os_yield(ms * USEC_PER_MS);
if ((ms <<= 1) > MS_PER_SEC)
ms = MS_PER_SEC;
goto loop;
}
/*
* CDB___db_tas_mutex_unlock --
* Release a lock.
*
* PUBLIC: int CDB___db_tas_mutex_unlock __P((MUTEX *));
*/
int
CDB___db_tas_mutex_unlock(mutexp)
MUTEX *mutexp;
{
if (!DB_GLOBAL(db_mutexlocks) || F_ISSET(mutexp, MUTEX_IGNORE))
return (0);
#ifdef DIAGNOSTIC
if (!mutexp->locked)
(void)write(STDERR_FILENO, MSG2, sizeof(MSG2) - 1);
mutexp->locked = 0;
#endif
MUTEX_UNSET(&mutexp->tas);
return (0);
}
#endif /* HAVE_MUTEX_TAS */
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